Medical devices may be coated so that the surfaces of such devices have desired properties or effects. For example, it may be useful to coat medical devices to provide for the localized delivery of therapeutic agents to target locations within the body, such as to treat localized disease (e.g., heart disease) or occluded body lumens. Localized drug delivery may avoid some of the problems of systemic drug administration, which may be accompanied by unwanted effects on parts of the body which are not to be treated. Additionally, treatment of the afflicted part of the body may require a high concentration of therapeutic agent that may not be achievable by systemic administration. Localized drug delivery may be achieved, for example, by coating balloon catheters, stents and the like with the therapeutic agent to be locally delivered. The coating on medical devices may provide for controlled release, which may include long-term or sustained release, of a bioactive material.
Aside from facilitating localized drug delivery, medical devices may be coated with materials to provide beneficial surface properties. For example, medical devices are often coated with radiopaque materials to allow for fluoroscopic visualization while placed in the body. It is also useful to coat certain devices to achieve enhanced biocompatibility and to improve surface properties such as lubriciousness.
Coated stent may be used to reduce restenosis rates in patients. Stents may be coated in a spraying process. For example, stents may be mounted into wire C-frames using stainless steel wire. The C-frame may then be mounted into a collet. The collet may be mounted into a shaft, and the shaft may be rotated, raised, and lowered across a spray plume.
Conventional coating methods may result in coating defects. Product specification for webbing may be restrictive, and only small webs may be allowable. For example, 70 μm web lengths may be cause for rejection. Some stents may be particularly prone to webbing of greater than 70 μm and protrusions of greater than 200 μm due to stent geometry (for example, the closeness of the struts).
Motor cars have been painted using vibrations to compensate for nozzle imperfections or other irregularities. Vibration may be imparted to the motor car during a spray painting operation by running the engine with one spark plug removed. The removed spark plug may induce vibration that may have the effect of smoothing the spray coating.
There is therefore a need for reducing coating defects in medical appliances.
Each of the references cited herein is incorporated by reference herein for background information.